Peripheral Blood Stem Cell Transplantation
What is peripheral blood stem cell transplantation?
Peripheral blood stem cell transplantation is a new
technique in which stem cells are obtained
from a patient's blood and used in bone marrow transplantation.
What are stem cells?
Stem cells are small, round cells with a squat nucleus and scant
surrounding cytoplasm. Although unremarkable in appearance, stem
cells can perform what have been called "acts of biological
resurrection."
What do stem cells do?
Whereas other types of cells in the body have a
limited lifespan and die after dividing their endowed number of
times, a stem cell can reproduce forever. The stem cell is immortal
(in cellular terms).
A stem cell can forgo immortality and turn into an ordinary blood
cell, a red blood cell (an erythrocyte), a white blood cell (a
leukocyte), or a large cell (a megakaryocyte) that fragments into the
platelets needed for blood to clot.
What is the value of stem cells for transplantation?
A relatively small number of stem cells can miraculously repopulate the
whole bone marrow, provide an endless supply of stem cells,
reconstitute the entire repertory of blood cells, and restore the
immune system.
Where do the stem cells come from for transplantation?
Under normal circumstances, stem cells are rarely seen in the blood stream. To recruit enough stem cells into the blood, stem cells are lured out of the bone marrow by a special regimen of drugs and coaxed into entering the peripheral blood (the blood stream).
How are the stem cells removed from the blood?
The blood is filtered
through a machine and the stem cells are skimmed off. The removal of
the cells is termed pheresis or apheresis (from the Greek
"aphairesis" for removal).
The stem cells then may be used right away for bone marrow
transplant or stored in liquid nitrogen until needed.
How is the patient "prepared" for the transplantation?
Before the transplant is done, the patient receives high-dose
chemotherapy and/or radiation therapy to destroy diseased cells (the
leukemic cells, lymphoma cells, solid tumor cells, the diseased
immune system cells in scleroderma, etc.) The stem cells are then
returned to the patient, where they can produce new blood and immune
cells and replace the cells destroyed by the treatment.
How is the transplantation actually done?
The stem-cell
preparation is infused into a vein and, once there in the blood
stream, the stem cells act like homing pigeons and head straight for
the bone marrow space.
Last Editorial Review: 4/15/2002
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